When I ask entrepreneurs and small business owners, it is not unusual for not having any marketing plan. I once read that Sir Richard Branson never had any marketing plan when he started the 1st Virgin business many years ago. In fact in one study of entrepreneurship (I couldn't recall the name of the study) was that as much as 50% of entrepreneurs and business owners don't have a business plan and marketing plan when they first started the business.
Customer Segment _ this is talked about most of the time, but let's accept the fact that today's customers are fragmented to smaller niches. Your product and service will not be consumed by only one segment and at critical mass. it is likely to be consumed by smaller segment and multi. No more critical mass, but rather a solid spread of niches. For example, who buys iPod's today? If Apple only think about yuppies they are making a big mistake because apparently iPod is also used by women and people with active lifestyle. Another example, who buys from hypermarket? If hypermarket only focuses on households they may not survive or be successful like today. Hypermarket main segment is actually small business restaurant operators that buy in larger quantity compare to households and on daily basis. I've been there, I know! LOL